puzzlewidget.h Example File
draganddrop/puzzle/puzzlewidget.h

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 #ifndef PUZZLEWIDGET_H
 #define PUZZLEWIDGET_H

 #include <QList>
 #include <QPoint>
 #include <QPixmap>
 #include <QWidget>

 class QDragEnterEvent;
 class QDropEvent;
 class QMouseEvent;

 class PuzzleWidget : public QWidget
 {
     Q_OBJECT

 public:
     PuzzleWidget(QWidget *parent = 0);
     void clear();

 signals:
     void puzzleCompleted();

 protected:
     void dragEnterEvent(QDragEnterEvent *event);
     void dragLeaveEvent(QDragLeaveEvent *event);
     void dragMoveEvent(QDragMoveEvent *event);
     void dropEvent(QDropEvent *event);
     void mousePressEvent(QMouseEvent *event);
     void paintEvent(QPaintEvent *event);

 private:
     int findPiece(const QRect &pieceRect) const;
     const QRect targetSquare(const QPoint &position) const;

     QList<QPixmap> piecePixmaps;
     QList<QRect> pieceRects;
     QList<QPoint> pieceLocations;
     QRect highlightedRect;
     int inPlace;
 };

 #endif